An automatic brake system is the conventional widespread means for braking a locomotive-hauled train of passenger coaches or cars. The automatic brake system enjoys widespread use by virtue of the fact that it is structurally simple, that it can transmit the braking order relatively fast, and in the event of the vehicles of the train being separated from one another in an accident, that it can automatically apply the brakes of the entire train. Meanwhile, increased train speeds and the introduction of automatic train control systems or automatic train operation systems raise the demand for better equipment than the conventional automatic brake system. Meeting this demand, a brake system primarily based on electric control or a direct-acting brake system coupled therewith has been made practically available. It is well known that when a vehicle is equipped with direct-acting brakes, it is necessary to provide an electrical braking order line in addition to the main air reservoir pipe in the longitudinal direction of the train. This system has the drawback that the brake will not work when the vehicles constituting the train are separated from one another. For this reason it has been considered necessary to provide an automatic brake system as a backup system when a vehicle is equipped only for direct-acting braking, and also it has been considered necessary to provide the automatic brake system in a vehicle equipped only for the direct-acting braking when a vehicle equipped only for the automatic braking is mixed in a train. In such case, however, two parallel piping systems have to be provided in the train, that is, the main air reservoir pipe for direct braking and the brake pipe for automatic braking.
These air pipes must necessarily be connected or disconnected together when the vehicles are coupled or uncoupled. This requires a substantial amount of time and labor, particularly in the case of a train which needs frequent shunting.